/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformMemory.h
Various memory regions that can be used with memory stats. The exact meaning of the enums are relatively platform-dependent, although the general ones (Physical, GPU) are straightforward. A platform can add more of these, and it won't affect other platforms, other than a minuscule amount of memory for the StatManager to track the max available memory for each region (uses an arrayFPlatformMemory::MCR_MAXbig)
enum EMemoryCounterRegion { MCR_Invalid, MCR_Physical, MCR_GPU, MCR_GPUSystem, MCR_TexturePool, MCR_StreamingPool, MCR_UsedStreamingPool, MCR_GPUDefragPool, MCR_PhysicalLLM, MCR_MAX, }